Supramolecular Self-Assembly of Dimeric Dendrons with Different Aliphatic Spacers

A series of low-molecular-mass organogelators (LMOGs), dimeric dendrons based on natural amino acids, glycine. and aspartic acid, with different aliphatic spacers have been synthesized and their self-assembly behavior and structure-property relationship have been studied. Transmission electron microscopy (TEM), atomic force microscopy (AFM), infrared spectroscopy (IR), and small-angle X-ray scattering (SAXS) were employed to characterize the self-assembled structures and to examine the effect of the length of aliphatic spacers on the gelation. It was found that all of the gels were thermoreversible and stable for more than half a year at room temperature. The dimeric dendrons with longer aliphatic spacers displayed enhanced gelation ability. The SAXS patterns of the xerogels G2SnG2 (n = 6, 8, and 10) showed periodical reflections that could be attributed to the formation of a hexagonal columnar phase, whereas G2S15G2 formed a lamellar structure. Hydrogen bonding and pi-pi stacking interactions were evidenced by IR and fluorescence spectroscopy with pyrene as a probe, respectively. Moreover, the compounds G2SnG2 not only acted as efficient organogelators but also self-organized into thermotropic liquid crystal, with the mesophase formation being correlated to the spacer length.